Trade SDMP/Finney7 - Driving a Geep?

[Steph Dale]

I thought I'd better post a quick message to give you guys some news.

The first production frets for the Markits-based gearboxes are here, I'll be doing some test building, instructions and then ordering a batch of gears for them.

Included was a further batch of hornguides, so if there are any outstanding requests from Cleckheaton I will be able to fulfill orders now.

And the bad news? I found out today that Mashima have discontinued production of the excellent and usefully-compact 1824. Not only will this cause real problems for fans of small 0-6-ot locos, it also scuppers a great deal of work that I've been puting in to developing sprung/compensated 4-wheel diesel bogies. Alternatives will be found, but unless I have a significant flash of inspiration they're likely to be somewhat less compact and may have to resort to Delrin chain to couple the axles. This latter point may not be as much as a problem as you might imagine if the bogie is carefully designed...

Steph

 

[flexible_coupling]

Steph - I was under the broad (and quite possibly incorrect) impression that the popular Delrin cog-and-chain components were no longer being manufactured? Or is that a case of chinese whispers/particular suppliers having issues...?

 

[alcazar]

I think there were supply problems earlier in the year, which I understand are now solved?

 

[Steph Dale]

You're both correct; there is currently no problem with supply of Delrin drive components.

Steph

 

[SteveO]

Steph, such a shame about the 1824s – almost the perfect size for bogie-mounted drives. Does anyone have any stock? I bought quite a few of them over the last year as I planned to use them exclusively on my kit builds.

I was in contact with a chap in Poland who was going to get back to me once he had a new supply in. I'll chase him up as his prices were good and delivered quickly.

 

[Dog Star]

Steph,

What is the position with regard to motors / gearboxes / drive components for diesel motor bogies? We have a Class 158 that is spluttering to life and I do not feel much like mounting the motor "mid-floor" with a long cardan shaft.

regards, Graham

 

[Steph Dale]

Graham,

Sorry for the delay in replying. I'm still investigating the use of a centrally mounted/cardan drive system, but haven't had much time to continue the work. One problem is productionising it - there's no point developing it if people aren't going to be able to get it working properly.

I have been occasionally looking in other areas and the question around low-profile self-contained drive bogies has been raised by a client, the results of which are below. This uses a modified and ball-raced version of the Wayoh coach bogie with Easybuild cosmetic parts. The wheels are Peartree, gearbox one of mine (13:1, with 10mm mounting centres) and the motor a Mashima 1430. It's a good fit in here and the performance equivalent to the erstewhile 1824. This bogie is yet to be run in, but I have every confidence; the motor is one I have used a lot in my HO models and the odd one or two heavy whitemetal locos use these and can pull the side off a house, even at modest gear ratios.

It represents a solution in something like a 158 as it won't intrude on the interior. The drive 'pack' size is small and the motor, gearbox and Delrin chain should easily fit into a bogie with inside frames. I'm assuming you've got the Nationalised Railways kit, so it's brass? In this form you may need one powered bogie per vehicle depending upon what you're asking the model to do, but then that's what the prototype has...

The build you see here started off as a complete, built set of bogies with nut-and-bolt construction, which seems to work well. I then raised the centre bolster/pivot on the driven bogie and made a loop for the back of the motor to pass through to stop it flapping about. Wiring in the pickups was the most tricky part of the job, although that was probably a close second with the tensioning 'skid' for the chain drive.

Steph

 

[Engineer]

Thanks for illustrating the bogie drives in post 262 - most interesting, will watch for future developments.

Just a footnote, a bit off-topic, having noticed mention in post 260 of motor bogies for diesels, and the challenges of cardan shafts - agreed, very hard to obtain a good solution and not a good option for consistent commercial production, for sure.

I put together a 'proof-of-concept' a year or two ago, to see if I could get a single motor, eight-wheel drive into a 7mm Met. Bo-Bo without compromising the clear space between the bogies. Pictures illustrate the test rig at a couple of stages of development. Worked well, adjusted to get the right scale speed range and extremely good hauling capability.

Work prevents me from doing more though one day I would like to experiment with an uprated version that could be tested more intensively, as well as an alternative configuration suitable for EMU stock, using underfloor space. Must emphasise that this is for my private pleasure, never a commercial development.

Generally, the shaft drive is not a development path I'd recommend unless engineering interest is more important than completing models!

 

[Steph Dale]

I've certainly nailed the use of shaft drive within a diesel bogie, with a Mk2 of the system due for release early next year. The problems come with trying to replicate the sorts of drives found in European or American HO scale r-t-r, where you either need loads of gears or transfer boxes.

I quite like your solution, but would not have used the top transfer box. Instead I'd mount the motor lower, which would not only hide it better but also cut out the potential inefficiency of the transfer box.

I am looking at using belt drives to provide a transfer box; it's an approach which works well, and quietly, in US outline 0-scale brass diesels. Productionising gear-based transfer boxes is tricky; even small errors in assembly can dramatically reduce efficiency and raise noise levels. So saying, I have used the Exactoscale transfer boxes in HO locos and see no reason why they shouldn't work with my, or any other, shaft drive.

The 8'6" bogies for diesels will come out in the new year. They're sprung and should be able to take a variety of drives, Delrin chain as shown above or with a larger, vertically-mounted motor and also, yes, with shaft drive...

But that's all later, the first job is to do some testing on the DMU bogie and then I need to get in touch with Ace kits to see about ordering* an ex-Meteor LSWR T1 0-4-4t, to help with prototyping. A small number of people on the forum will now be getting sweaty palms...

Steph

*29 Sept mini-update; T1 kit now ordered. I'd better find some time to finish off some CAD work hadn't I...?

 

[Steph Dale]

I hope to be able to publish some feedback from the client in due course - there's nothing quite like an independent opinion. But, I have to say the trials with the 8'6" DMU bogie over the last couple of days have been very positive. I should also add that none of the mechanism has not yet been lubricated; that will be advised for the client to do after painting and weathering and before running in.

So; it's very quiet. I test run on a length of track nailed straight on to a board deliberately so I can hear what's going on. Other than a quiet purr from the motor (more related to the KPC controller's resonant frequency than anything else) it's pretty much silent. The speed is controllable and smooth with power aplenty. With compensation designed in to the Wayoh bogie the pickup and adhesion is good - running will be reliable. The ball races will also help, of course.

I'm happy to publish the dimensions/mods and get the gearbox into production, I'm just wondering who would want one...? Parts? Kit? Ready to roll?

Graham?

Steph

 

[SimonT]

Well my ancient 103 is due a Heavy, so count me in for a box of bits.
Simon

 

[Dikitriki]

2 x box of bits - although depending on the premium, I may go RTR.

Richard

 

[Steph Dale]

Now here's something a bit different...

It's called the RQN. Why, well because it's Really Quite Narrow. A gearbox designed for locos that have to have drive on the same axle you want to hang a set of inside motion on. It doesn't matter whether it's an Atlantic, an 0-4-4t or a Midland Spinner this should fit and give you both drive, at 40:1 using a Canon 1833 or perhaps Mashima 18xx, and either a set of four eccentrics or a pair of eccentrics and cranks.

Minimum crank centres are yet to be determined, but look to be somewhere between 14.5 and 15mm; they can be larger. For locos with Stephenson valvegear only the outer (usually forward gear) eccentrics are provided requiring the motion to be slightly simplified. Clearances are set for use with Laurie Griffin cranks and eccentrics.

Anyway, here's a sketch, showing the gearbox and the minimum width of cranks/eccentrics using Laurie's parts. Eventually I'll do a machining diagram for those using custom wheels/axles:

The planning template may well have uploaded below here as well. I've now got the artwork ready to go to the etchers ready for a test build. This gearbox will not be available for self-assembly, only ex-works assembled to order. It's just too tricky for me to write the instructions and it does require customised gear sets.

I should be picking up a suitable kit for a test build sometime this week, more shortly...

Steph

Edit - removed underscaled attachment.

 

[7mmMick]

The RQN looks great Steph and i'm looking forward to seeing how your build progresses. The completion of this gearbox may well see a long time shelf queen of mine rise from the ashes ? Here's how far I am with the frames, which really isn't very far at all. I made the horn guides up so as to give myself maximum room so I'm hoping the RQN will fit the bill?





Gloomy today, hopefully before long all that space will be full of wobbly bits and 67337 will be born

ATB Mick

 

[Steph Dale]

Mick,
If my mental arithmetic holds up this evening the width across the outside of the cranks when made up straight out of the Laurie Griffin packets is around 21-21.5mm. So in your case it might be worth finding out what the prototype's cylinder centres are. Worth checking your other key chassis dimensions, such as sideplay as you can't have any sideplay on the driven axle - the valvegear will jam.
BTW - the above sketch is only the 'proof of concept' as I'm currently investigating a number of methods for getting the gearbox together. It just gives you guys an early awareness that I'm working on it. There is just one other feature I'm currently working out how to implement and then I'm tempted to give it a whirl and see what happens.
Steph

p.s. updated (full size!!!) planning template attached, feel free to let me know how it fits!

 

[Scale7JB]

Mick, do you plan to use the eccentrics on the valve gear?

JB.

 

[7mmMick]

Mick, do you plan to use the eccentrics on the valve gear?

JB.

I was hoping to but it may prove difficult?

Mick,
If my mental arithmetic holds up this evening the width across the outside of the cranks when made up straight out of the Laurie Griffin packets is around 21-21.5mm. So in your case it might be worth finding out what the prototype's cylinder centres are. Worth checking your other key chassis dimensions, such as sideplay as you can't have any sideplay on the driven axle - the valvegear will jam.
BTW - the above sketch is only the 'proof of concept' as I'm currently investigating a number of methods for getting the gearbox together. It just gives you guys an early awareness that I'm working on it. There is just one other feature I'm currently working out how to implement and then I'm tempted to give it a whirl and see what happens.
Steph

p.s. updated (full size!!!) planning template attached, feel free to let me know how it fits!

Right Steph, I printed off the pdf document and have done some drawing/measuring etc. Working from these dimensions and using the bottom of your two drawings ;

LG Stephenson inside motion;
NER pattern cranks OD 6.5mm
Eccentrics OD 3.9mm
Gearbox OD 8mm

So altogether on the driven axle you have 28.8mm OD and I have an inside hornblock measurement of 24.7mm. So looking at this you would have to loose just over 2mm per side, which I think would be quite straight forward as the NER crank webs are quite meaty.

The only issue then is the cylinder centres are far too wide. I don't have a drawing of the G5 valve gear but off the top of my head the cylinder centres need to be around 14-15mm to accommodate the NER slide bars and at the minute we're about 22mm??

I would have thought the only option is to really thin down the crank webs and off set the connecting rod's position in the slide bar so that the joggle allows the cylinder centres needed. I would also have thought that the eccentrics would have to have a joggle introduced as close to the axle as possible to bring them back to the centre position?

I know this is not fantastic engineering but the driven axle is not really seen and it is the movement of the slide bars and valves that is paramount IMO. To that end I suppose it's not essential that the crank webs are of NER pattern or what they look like for that matter, as long as they supply the correct movement for the connecting rods ?

With some jiggery pokery I think it will work a treat

Here's the void that will be filled and although the footplate still has material across at the front of the tanks even with this removed I don't think from normal viewing angles you will see the driven axle?



Collecting dust like all good shelf queens

ATB Mick

 

[Steph Dale]

Mick,
If you use the lower diagram on the sheet the dotted lines show the centres of the cranks at minimum centres using unmodified LG parts. With that you get a pair of eccentrics between the cranks and gearbox. And 21.5mm overall width.
So, you can either assemble the motion on a single eccentric with simplified movement, or I can put a mounting point on the gearbox itself to simulate the inner (reverse gear) eccentrics if you want the full movement of the expansion link. If you've got a GA or MA then the position of the mounting can be worked out with some accuracy to allow forward gear movement of the motion.
It probably is worth getting it as right as possible as you may be able to see cranks etc in a side view of the loco, especially in forward gear with the expansion link dropped. With a long frame M7 you can also see the balance weights on the extended cranks, so the appearance has been much in mind!
Steph

 

[7mmMick]

Mick,
If you use the lower diagram on the sheet the dotted lines show the centres of the cranks at minimum centres using unmodified LG parts. With that you get a pair of eccentrics between the cranks and gearbox. And 21.5mm overall width.
So, you can either assemble the motion on a single eccentric with simplified movement, or I can put a mounting point on the gearbox itself to simulate the inner (reverse gear) eccentrics if you want the full movement of the expansion link. If you've got a GA or MA then the position of the mounting can be worked out with some accuracy to allow forward gear movement of the motion.
It probably is worth getting it as right as possible as you may be able to see cranks etc in a side view of the loco, especially in forward gear with the expansion link dropped. With a long frame M7 you can also see the balance weights on the extended cranks, so the appearance has been much in mind!
Steph

Absolutely Steph, I would like my G5 to be as close to right as possible. I shall have to source a suitable drawing nearer the time, forward gear is certainly preferential so it sounds like there is ample room and no real need for major compromise?

ATB Mick

 

[Steph Dale]

Absolutely Steph, I would like my G5 to be as close to right as possible. I shall have to source a suitable drawing nearer the time, forward gear is certainly preferential so it sounds like there is ample room and no real need for major compromise?

ATB Mick

Mick,

That's very much the intention. The prototype model has ended up being an Adams LSWR T1 0-4-4t, which I suspect is probably around the same size as your G5 (23' overall wheelbase and 5'7" drivers). As you know the build is featured on my Southern workbench thread. As I start adding info there it may help you see what I've been intending to do.

Having a GA or MA will help when you start knitting the whirly bits of your loco; for a start you'll be able to copy off the dimensions of the motion parts. It'll also help me with positioning of the anchor that deputises for the inner pair of (reverse) eccentrics to give you something suitably neat. Even if you can't find a directly suitable drawing, we may be able to deduce enough to get it right: As an example, neither the MA or GA for the T1 survive as far as I can tell, but I have a full set of dimensions of the key parts as they're common to Adams A12 0-4-2 tender locos.

Steph